One of the OAM function types used for fault management (see also CC, RDI).
ANSI
|
American National Standards Institute.
ASCII (American Standard Code for Information Interchange)
|
A seven-level code (128 possible characters) used for data transfer.
ATM (Asynchronous Transfer Mode)
|
A standard (ITU) implementation of cell relay, which is a packet switching technique using packets (cells) of a fixed length. It is asynchronous in the sense that the recurrence of cells containing information from an individual user is not periodic. ATM is used for transmission of integrated services, broadband switching and multiplexing with high-performance and cost-effectiveness under certain QoS guarantees.
Backhaul
|
Transporting traffic between distributed sites (typically access points) and more centralized points of presence. See Cellular Backhaul.
Bandwidth
|
The range of frequencies passing through a given circuit. The greater the bandwidth, the more information can be sent through the circuit in a given amount of time.
Best effort
|
A QoS class in which no specific traffic parameters and no absolute guarantee are provided. Best effort includes UBR and ABR.
Bit
|
The smallest unit of information in a binary system. Represents either a one or zero (“1” or “0”).
Bit Interleaving /Multiplexing
|
A process used in time division multiplexing where individual bits from different lower speed channel sources are combined (one bit from one channel at a time) into one continuous higher speed bit stream.
bps (Bits Per Second)
|
A measure of data transmission rate in serial transmission.
Bridge
|
A device interconnecting local area networks at the OSI Data Link Layer, filtering and forwarding frames according to media access control (MAC) addresses.
Bridging
|
Interconnecting local area networks at the OSI Data Link Layer, filtering and forwarding frames according to media access control (MAC) addresses.
Carrier Ethernet is a ubiquitous service based on standardized equipment and protocols providing seamless connectivity between high speed Ethernet-based LANs and WANs. Carrier Ethernet is characterized by industry-defined attributes for service level agreements, provisioning, system-wide management, and carrier-class OAM. Originally implemented in the core network, Carrier Ethernet is now being extended to the edge and access segment.
Carrier Ethernet deployment is picking up pace as Ethernet becomes a widely-accepted, carrier-grade service suite, however, it depends on service providers’ ability to cost-effectively overcome two key challenges: The diversity of existing access and transport networks, and the need to meet user expectations for SLA accountability.
Central Office (CO)
|
Telephone company switching office. This is where you would find the local telco switch that connects to your telephone.
Channel
|
A path for electrical transmission between two or more points. Also called a link, line, circuit or facility.
Channelized T1/E1
|
T1 or E1 service that is divided into individual 64 kbps channels (or channels that are multiples of 64 kbps such as a 256 kbps channel made from four 64 kbps channels), as opposed to unchannelized service, which uses the entire bandwidth of the T1 (1.544 Mbps) or E1 (2.048 Mbps). Channelized T1 or E1 lines can consist of switched lines with in-band signaling or leased lines.
CIR (Committed Information Rate)
|
A term used in Frame Relay, which defines the information rate that the network is committed to provide to the user, under any network conditions.
Circuit Emulation
|
A connection over a virtual circuit-based network providing service to the end users that is indistinguishable from a real point-to point, fixed-bandwidth circuit. Services based on circuit emulation (Circuit Emulation Services or CES) offer traditional TDM trunking (at n x 64 kbps, fractional T1/E1, T1/E1 or T3/E3) over a range of transport protocols, including ATM, Internet Protocol (IP), MPLS and Ethernet.
Circuit Emulation Service
|
New technology for offering circuit emulation services over packet-switched networks. The service offers traditional TDM trunking (at n x 64 kbps, fractional E1/T1, E1/T1 or E3/T3) over a range of transport protocols, including Internet Protocol (IP), MPLS and Ethernet.
CO (Central Office)
|
Telephone company switching office. This is where you would find the local telco switch that connects to your telephone.
CPE (Customer Premises Equipment)
|
Generally refers to communications equipment located at the customers' premises for use with communication service providers' services. In some cases, these are customer-owned or leased; in other cases, these are the property of the service provider.
Data Link Layer
|
Layer 2 of the OSI model. The entity, which establishes, maintains, and releases data-link connections between elements in a network. Layer 2 is concerned with the transmission of units of information, or frames, and associated error checking.
DiffServ or DS (Differentiated Services)
|
QoS method to differentiate and control IP traffic so that the traffic’s relative priority can be determined on a per-hop basis.
DSCP (Differentiated Services Code Point)
|
A field in the header of IP packets for packet classification purposes.
DS0 (Digital Subscriber Level Zero)
|
A 64 kbps unit of transmission bandwidth. A worldwide standard speed for digitizing one voice conversation, and more recently, for data transmission. Twenty-four DS0s (24 x 64 kbps) equal one DS1.
DS1 (Digital Signal Level 1) Channel
|
Framing specification used in transmitting digital signals at 1.544 Mbps on a T1 facility or 2.048 Mbps on an E1 facility.
DS2 Channel
|
For a T1 line, a 6.312 Mbps channel that consists of four DS1 channels; for an E1 line, an 8.45 Mbps channel that consists of four DS1 channels.
DS3 Channel
|
A 44.736 Mbps line consisting of seven DS2 channels. A DS3 line is also called a T3 line.
DSL (Digital Subscriber Line)
|
A modem technology for transmitting information at high speeds on existing copper phone lines to homes and businesses. DSL operates over existing copper telephone lines and requires runs of usually less than 20,000 feet to a central telephone office. Types of DSL include asymmetric DSL (ADSL), symmetric DSL (SDSL), high-bitrate DSL (HDSL) and the latest, symmetric high-bitrate DSL (SHDSL).
E1
|
A 2.048 Mbps line, common in Europe, that supports thirty-two 64 kbps channels, each of which can transmit and receive data or digitized voice. The line uses framing and signaling to achieve synchronous and reliable transmission. The most common configurations for E1 lines are E1 PRI, and unchannelized E1.
E1 MLPPP (Multilink Point-to-Point Protocol)
|
Combining (bonding) multiple PPP (Point-to-Point Protocol) links between two systems into one logical data pipe. MLPPP is a standard IETF protocol.
E3
|
The European standard for high speed digital transmission, operating at 34 Mbps.
EFM Ethernet in the First Mile (also known as IEEE 802.3ah)
|
A collection of protocols specified in IEEE 802.3, defining Ethernet in the access networks, i.e. First/Last Mile. EFM also addresses other issues required for mass deployment of Ethernet services, such as operations, administration and maintenance (OAM) and compatibility with existing technologies (e.g. spectral compatibility for copper).
E-LAN (Ethernet Local Area Network)
|
A Fast Ethernet or Gigabit Ethernet service used for multipoint-to-multipoint transparent Ethernet LAN connectivity, allowing any location to speak with any other location in a customer’s Metro Ethernet network (see MEF).
E-Line (Ethernet Line)
|
A service providing a point-to-point Ethernet Virtual Connection (EVC) between two customer user interfaces or two locations in a Metro Ethernet network (see MEF).
Encapsulation
|
Encapsulating data is a technique used by layered protocols in which a low level protocol accepts a message from a higher level protocol, then places it in the data portion of the lower-level frame. The logistics of encapsulation require that packets traveling over a physical network contain a sequence of headers.
Enterprise Network
|
An information infrastructure, often combining private and public facilities, to cover all of the locations operated by a single company or corporate enterprise with a single communications fabric.
Ethernet
|
Most popular local area network (LAN) technology in use today. All stations on the LAN share the total bandwidth, which is at speeds of 10 Mbps (Ethernet), 100 Mbps (Fast Ethernet), or 1000 Mbps (Gigabit Ethernet).
A key element in Carrier Ethernet transport and services, Ethernet demarcation provides a clear separation between the user and the network, allowing carriers to extend network visibility up to the user premises.
Ethernet signal degradation typically limits Ethernet cable runs to 100 meters (328 feet). To achieve longer distances, an Ethernet extender is required. These devices can be used to drive Ethernet up to 5.5 kilometers over copper and more than 100 kilometers over fiber.
RAD Data Communications has a wide range of Ethernet modems with combined E1/T1 multiplexing capabilities for point-to-point Ethernet extension over any type of infrastructure or media.
Ethernet OAM (Operation, Administration and Maintenance) is a set of functions designed to monitor network operation in order to detect network faults and measure its performance. Carrier-class Ethernet services require automated end-to-end management and monitoring, including OAM capabilities such as connectivity verification, fault detection, performance monitoring, and alarm indication.
Ethernet over PDH (Plesiochronous Digital Hierarchy) is a method for carrying Ethernet traffic over PDH network lines such as E1/T1 or E3/T3. It is one of several technologies available to service providers who wish to offer new carrier-class Ethernet services over existing legacy infrastructure.
Although SDH networks were originally engineered to transport voice traffic, many carriers are using their ubiquitous SDH infrastructure to deploy Ethernet services. Recent developments in Next Generation SDH have made these networks more cost-effective and "user friendly" for Ethernet traffic.
Although SONET networks were originally engineered to transport voice traffic, many carriers are using their ubiquitous SONET infrastructure to deploy Ethernet services. Recent developments in Next Generation SONET have made these networks more cost-effective and "user friendly" for Ethernet traffic.
One of the key attributes of Carrier Ethernet services, by which the service provider offers business users bandwidth, delivery, and performance guarantees for selected traffic, and allocates the necessary network resources accordingly.
A fiber media converter connects standard optical interfaces with electrical interfaces; links single mode fibers with multimode fiber cables; adapts dissimilar data rates; and converts different transmission protocols such as TDM E1/T1 and Ethernet.
Fiber Optics
|
A transmission medium consisting of thin glass or plastic filaments. Light beams (generated by an LED or laser) travel through the fiber optic line, carrying large amounts of data over long distances.
Fiber optic modulator/demodulators (modems) enable E1/T1, E3/T3, LAN, and data extension over fiber optic infrastructure.
Fiber Optic Multiplexers
|
Fiber optic multiplexers are devices that combine multiple signals for transport on a common transmission path. RAD’s fiber optic multiplexers enable transmission of E1 or T1 channels, E3 or T3 tributaries and wire-speed Ethernet over a fiber optic link. A fiber optic multiplexer at the other end reverses the process.
Fractional T1 Line
|
A T1 line that contains both switched and nailed-up channels. T1 PRI and ISDN BRI lines can also be Fractional T1 lines.
Frame
|
A logical grouping of information sent as a link layer unit over a transmission medium. The terms packet, datagram, segment and message are also used to describe logical information groupings.
Frame Relay
|
An efficient packet switching technology providing high speed frame or packet transmission with minimum delay and efficient bandwidth utilization over virtual circuits. The link layer handles much of the network layer functionality. It has less protocol overhead than X.25.
Framing
|
At the physical and data link layers of the OSI model, bits are fit into units called frames. Frames contain source and destination information, flags to designate the start and end of the frame, plus information about the integrity of the frame. All other information, such as network protocols and the actual payload of data, is encapsulated in a packet, which is encapsulated in the frame.
Full Duplex
|
A circuit or device permitting transmission in two directions (sending and receiving) at the same time.
An ITU-T standard specifying the Synchronization Status Message (SSM) format for Synchronous Etherent.
Gateway
|
Gateways are points of entrance and exit from a communications network. Viewed as a physical entity, a gateway is that node that translates between two otherwise incompatible networks or network segments. Gateways perform code and protocol conversion to facilitate traffic between data highways of differing architecture.
Gigabit Ethernet converters typically link copper cabling (UTP) with fiber optics or multimode fiber with single-mode fiber cables, to enable transport of Gigabit Ethernet traffic over diverse media.
GFP (Generic Framing Procedure)
|
Defined by ITU-T G.7041, generic framing procedure allows efficient mapping of variable length, higher-layer client signals, such as Ethernet, over a transport network like SDH/SONET. Recently, GFP has been extended to lower speed PDH networks.
Grooming
|
In telecommunications, the process of separating and segregating channels by combing, such that the broadest channel possible can be assembled and sent across the longest practical link. The aim is to minimize de-multiplexing traffic and reshuffling it electrically.
G.SHDSL, or SHDSL, is a standardized method (ITU-T G.991.2) to transport symmetrical data rates on copper pair access lines. G.SHDSL offers bitrates from 192 kbps to 2.3 Mbps over a 2-wire single pair and up to 9.2 Mbps over four bonded pairs.
A G.SHDSL modem is a customer located transceiver, connecting users to a G.SHDSL service via the local DSLAM.
HDLC (High-level Data Link Control)
|
A synchronous, bit-oriented link layer protocol for data transmission. Frame Relay is an example of an HDLC-based packet protocol.
HDSL (High Bit-Rate Digital Subscriber Line)
|
A high performance twisted pair transmission technology, best known as an enhanced transport mechanism for T1 or E1 service. It is designed for the Local Loop between a customer’s premises and an area exchange central office.
IEEE (Institute of Electrical and Electronic Engineers)
|
An international professional society issuing its own standards. The IEEE is a member of ANSI and ISO.
IETF (Internet Engineering Task Force)
|
Body which was initially responsible for developing the specifications required for the interoperable implementation of IP.
IMA (Inverse Multiplexing over ATM)
|
A method to pass ATM traffic over multiple E1/T1 links while keeping the ATM’s quality of service and optimization of bandwidth usage.
In-band Signaling
|
The transmission of signaling information over the same path as data and/or voice information. Another term for in-band signaling is robbed-bit signaling. Robbed-bit refers to the 8 kbps of each channel used for signaling. T1 access lines containing one or more switched channels, and switched-56 lines use in-band signaling.
Interface converters are devices that convert physical media, data rates and transmission protocols, allowing service interworking between different communication interfaces
A method in which the inverse multiplexer slices the data stream into equal portions and transmits each portion over an available circuit. The receiving end adjusts for network-induced delay and reassembles the data packets into their proper order. Therefore, an inverse multiplexer allows lower speed channels across a network to be combined into a single, higher speed data stream.
IP (Internet Protocol)
|
A networking protocol for providing a connectionless service to the higher transport protocol. It is responsible for discovering and maintaining topology information and for routing packets across homogeneous networks. Combined with TCP, it is commonly known as the TCP/IP platform.
IP Address
|
Also known as an Internet address. An IP address (Internet Protocol address) is a unique reference number used by devices attached to a network when sending information through a Local LAN, Wide area WAN or the Internet networks.
A central office (CO) device for delivering digital subscriber line services that link DSL connections to a single high-speed broadband (IP) line.
IP Telephony
|
The transmission of voice over an Internet Protocol (IP) network. Also called Voice over IP (VoIP), IP telephony allows users to make phone calls over the Internet, intranets, or private LANs and WANs that use the TCP/IP protocol.
ISDN (Integrated Services Digital Network)
|
A carrier-provided service that allows a variety of switched digital data and voice transmissions to be accommodated simultaneously. ISDN is available as BRI, PRI and B-ISDN.
ISDN BRI (Basic Rate Interface) Line
|
An ISDN line that uses two B-channels for user data, and one 16 kbps D-channel for signaling. Both B-channels can be switched or nailed up, or one channel can be switched and the other nailed up. A line of this type can connect to standard voice service, switched 56 kbps data service or switched 64 kbps data service.
ISDN PRI (Primary Rate Interface) Line
|
An ISDN interface providing 23 B-channels, each operating at 64 kbps, and a single D-channel also operating at 64 kbps to customer’s premises.
ITU (International Telecommunication Union)
|
A European-based, international advisory committee recommending worldwide standards for transmission.
Jitter
|
The deviation of a transmission signal in time or phase. It can introduce errors and loss of synchronization in high speed synchronous communications.
Jitter Buffer
|
Variation in the arrival times between packets, also called jitter, causes unnatural-sounding voice instead of a smooth voice stream. If a packet does not arrive in time to fit into the voice stream, the previous packet is replayed. This can seriously detract from voice quality. Since the jitter buffer adds to the overall delay of voice transmissions, the optimal jitter buffer should fit the network's differential delay. Adaptive jitter buffering continuously monitors the network delay and adjusts the queuing period accordingly.
LAN (Local Area Network)
|
A network that interconnects devices over a geographically small area, typically in one building or part of a building. The most popular LAN type is Ethernet, a 10 Mbps standard that works with 10BaseT, 10Base2, or 10Base5 cables.
Last Mile
|
(Sometimes referred to as Local Loop). The final leg of delivering communications connectivity to a resident or customer. Typically seen as an expensive challenge because “fanning out” wires and cables is a considerably expensive and physically difficult task.
Latency
|
The time between initiating a request for data and the beginning of the actual data transfer. Network latency is the delay introduced when a packet is momentarily stored, analyzed and then forwarded.
LCAS (Link Capacity Adjustment Scheme)
|
A method to dynamically increase or decrease the bandwidth of virtual concatenated containers in SDH. The LCAS protocol is specified in ITU-T G.7042. It allows on-demand increase or decrease of the bandwidth of the virtual concatenated group in a hitless manner. This brings bandwidth-on-demand capability for data clients like Ethernet when mapped into SDH containers.
Leased Line
|
A permanent telephone connection between two points that is rented for exclusive use from a telecommunications common carrier. In contrast to a normal dial-up connection, a leased line is always active. Typically, the highest speed data connections require a leased line connection. For example, a T1 channel is a type of leased line that provides a maximum transmission speed of 1.544 Mbps.
Local Loop
|
(Sometimes referred to as Last Mile). The physical wires that run from the subscriber’s telephone set, PBX, or key telephone system to the telephone company’s central office. Increasingly, the Local Loop now goes from the main distribution frame at the customer premises to the telephone company. The subscriber is responsible for connecting his wires from the box at the customer’s premises to his phone, PBX, or key system.
Loopback
|
A type of diagnostic test in which the transmitted signal is returned to the sending device after passing through all or part of a communications link or network.
MAC (Media Access Control)
|
A protocol that defines the way workstations gain access to transmission media, most widely used in reference to LANs. For IEEE LANs, the MAC layer is the lower sublayer of the data link layer protocol.
MAC-in-MAC
|
An IEEE 802.1ah standard for layering the Ethernet network into customer and provider domains with complete isolation among their MAC addresses. It enables service providers to separate customer traffic from management traffic and also save on VLAN IDs.
MAN (Metropolitan Area Network)
|
A network that provides regional connectivity within a metropolitan area (such as a city).
MEF (Metro Ethernet Forum)
|
A non-profit organization chartered with the mission of accelerating the adoption of optical Ethernet as the technology of choice in future metro networks worldwide. Ethernet was chosen for its relative simplicity and popularity with end-users, as well as for lowering costs of Ethernet equipment.
MIB (Management Information Base)
|
A directory listing the logical names of all information resources residing in a network and pertinent to the network’s management. A key element of SNMP management systems.
MLPPP (Multilink PPP)
|
Connects multiple links between two systems as needed to provide extra bandwidth. Remotely accessing resources through MLPPP allows for an increase in overall throughput by combining the bandwidth of two or more physical communication links, such as analog modems, ISDN and other analog/digital links.
Modem (Modulator-Demodulator)
|
A device used to convert serial digital data from a transmitting DTE to a signal suitable for transmission over extended distances. It also reconverts the transmitted signal to serial digital data for acceptance by a receiving DTE.
MPLS (Multiprotocol Label Switching)
|
A standards-approved technology that allows core network routers to operate at higher speeds without needing to examine each packet in detail, allows more complex services to be developed, enabling discrimination on a QoS basis. MPLS speeds up network traffic flow by bringing Layer 2 information to Layer 3 (IP) and facilitating network management. It forwards traffic using a label that instructs the routers and the switches in the network where to forward the packets based on pre-established IP routing information. MPLS is called multiprotocol because it works with the IP, ATM, and Frame Relay network protocols.
Multimode Fiber
|
A fiber with a large core diameter. 50-200 microns compared with the wavelength of light. It therefore propagates more than one mode. With multimode fiber, light traverses multiple paths, some longer than others. This leads to dispersion, which reduces optical range at high bit rates.
Multiplexer (Mux)
|
A device allowing two or more signals to pass over and share a common transmission path simultaneously.
Network
|
(1) An interconnected group of nodes. (2) A series of points, nodes, or stations connected by communications channels; the collection of equipment through which connections are made between data stations.
Network Layer
|
A layer in the OSI reference model. The network layer provides address resolution and routing protocols. Address resolution enables the network layer to determine a unique network address for a node. Routing protocols allow data to flow between networks and reach their proper destination. Examples of network layer protocols are Address Resolution Protocol (ARP), Datagram Delivery Protocol (DDP), Internet Control Message Protocol (ICMP), Interior Gateway Protocol (IGP), Internet Protocol (IP), Internetwork Packet Exchange (IPX) and Packet Layer Protocol (PLP).
NMS (Network Management System)
|
The system that controls the network configuration, fault and performance management, and diagnostic analysis.
NNI (Network Node Interface or Network-to-Network Interface)
|
ITU-T standard interface between nodes within the same network. The ATM forum distinguishes between two standards, one for private networks called PNNI and one for public networks known as public NNI.
Node
|
A point of interconnection to a network.
OAM (Operation Administration and Maintenance)
|
A set of network management functions that provide for network fault and performance management, analysis and fault isolation. OAM functions exist in carrierclass TDM and ATM networks, but are now also being implemented in MPLS and Ethernet networks. These capabilities will provide the basic tools for carriers to monitor, diagnose, and troubleshoot first-mile Ethernet access links.
OSI (Open Systems Interconnection) Model
|
A seven-layer model of network communications developed by the International Organization for Standardization (ISO).
Out-of-Band Connection
|
A remote link, or a link outside connected networks, established over a modem. It is useful when network communications are not available.
Out-of-Band Signaling
|
The transmission of signaling information over a different path from data and/or voice information. CCS7 uses out-ofband signaling.
Packet
|
An ordered group of data and control signals transmitted through a network, as a subset of a larger message.
Packet Switching
|
A data transmission technique, which divides user information into discrete data envelopes called packets, and sends the information packet by packet.
Parity Bit
|
An additional non-information bit added to a group of bits to ensure that the total number of l bits in the character is even or odd.
Payload
|
The 48-byte segment of the ATM cell containing user data. Any adaptation of user data via the AAL will take place within the payload.
PBX (Private Branch Exchange)
|
A private telephone switching system, usually serving an organization, such as a business or a government agency, and is usually located on the customer’s premises.
PHY (Physical layer)
|
The bottom layer of the ATM protocol reference model, it is subdivided into two sublayers: Transmission Convergence (TC) and Physical Medium (PM). It provides ATM cell transmission over the physical interfaces that interconnect the ATM devices.
Physical Layer
|
Layer 1 of the OSI model. The layer concerned with electrical, mechanical, and handshaking procedures over the interface connecting a device to the transmission medium.
Policing
|
A method for verifying that the incoming VC complies with the user’s service contract.
PON (Passive Optical Network)
|
A high bandwidth, point-to-multipoint optical fiber network based on ATM, Ethernet or TDM. In this type of optical network, wavelengths of light are divided into timeslots so that each wavelength can be shared by a number of users. With PONs, a single fiber from the carrier’s exchange can service 16, 32 or more buildings through the use of both passive devices to split the optical signal, and PON protocols to control the sending and transmission of signals across the shared access facility.
PoP (Point of Presence)
|
An access point to the rest of the network.
Port
|
The physical interface to a computer, multiplexer, for connection of terminals and modems.
PPP (Point-to-Point Protocol)
|
Provides a standard means of encapsulating data packets sent over a single-channel WAN link. It is the standard WAN encapsulation protocol for the interoperability of bridges and routers over synchronous or asynchronous circuits.
Prioritization
|
Also called CoS (class of service), classifies traffic into categories such as high, medium, and low. The lower the priority, the more “drop eligible” is a packet. E-mail and Web traffic are often placed in the lowest categories. When the network gets busy, prioritization ensures critical or high-rated traffic is passed first, and packets from the lowest categories may be dropped.
Protocol
|
A formal set of conventions governing the formatting and relative timing of message exchange between two communicating systems.
Pseudowire
|
Point-to-point connections set up between pairs of Provider Edge routers. Their primary function is to emulate (typically layer 2) native services like ATM, Frame Relay, Ethernet, low-rate TDM, or SONET/SDH over an underlying common packet switched network (MPLS, IP, or L2TPv3) network core. To achieve this, each of these technologies is encapsulated into a common MPLS format. Pseudowires are defined by the IETF PWE3 (Pseudowire Edge to Edge Emulation) WG.
PSTN (Public Switched Telephone Network)
|
The telecommunications network commonly accessed by ordinary telephones, key systems, PBX trunks and data equipment.
Q-in-Q
|
See MAC-in-MAC.
QoS (Quality of Service)
|
Refers to the capability of a network to provide better service to selected network traffic over various technologies, including Frame Relay, Asynchronous Transfer Mode (ATM), Ethernet and 802.1 networks.
RADIUS (Remote Authentication Dial-In User Service)
|
An authentication, authorization and accounting protocol for applications such as network access or IP mobility. Many network services require the presentation of security credentials (such as a username and password or security certificate) in order to connect to the network. Before access to the network is granted, this information is passed to a network access server (NAS) device over the link-layer protocol, then to a RADIUS server over the RADIUS protocol. The RADIUS server checks that the information is correct using authentication schemes like PAP, CHAP or EAP.
RADview
|
The RADview Graphical User Interface (GUI) is an SNMP-based management system enabling complete monitoring and control of LAN and WAN networks from a central management station. The system provides direct on-line supervision, configuration and diagnostics.
Redundancy /Redundant Card or Power
|
Backup components used to ensure uninterrupted operation of a system in case of a failure.
Router
|
An interconnection device that connects individual LANs. Unlike bridges, which logically connect at OSI layer 2, routers provide logical paths at OSI layer 3. Like bridges, remote sites can be connected using routers over dedicated or switched lines to create WANs.
Routing
|
The process of selecting the most efficient circuit path for a message.
RSVP (Resource reSerVation Protocol)
|
A protocol developed for supporting different QoS classes for IP applications.
SDH (Synchronous Data Hierarchy)
|
The European standard for using optical media as the physical transport for high speed long-haul networks.
SFP
|
The Small Form-factor Pluggable (SFP) is a compact optical transceiver used in telecom and datacom applications. It is a popular industry format supported by most fiber optic component vendors. The primary advantages of this approach are hot pluggability, field replacabilty, and mix and match optical reach and type. Using the SFP platform, RAD has engineered a "System on an SFP" for extension of Ethernet and LAN over E1/T1 and E3/T3 connections.
SHDSL
|
SHDSL, (ITU-T G.991.2, Single-pair High-speed Digital Subscriber Line), is a standardized method of extending the range of copper telephone lines for broadband services. SHDSL technology is used to transport data symmetrically at rates of 192 kbps to 2.3 Mbps over 2-wire, or 384 kbps to 4.6 Mbps over 4-wire. The latest SHDSL standard is SHDSL.bis. Based on ITU-T G.991 and ETSI TS 101524, SHDSL.bis uses TC-PM 16 or TC-PAM 32 line coding and multi-pair bonding technology to reach transmission rates up to 5.69 Mbps on 1 pair (2-wire) for a rate up to 22.8 Mbps over 8-wire.
Single Mode
|
Describing an optical wave-guide or fiber that is designed to propagate light of only a single wavelength (typically 5-10 microns in diameter).
SLA (Service Level Agreement)
|
A formal negotiated agreement between customers and their service provider, or between service providers. It records the common understanding about services, priorities, responsibilities, guarantees, etc. with the main purpose to agree on the level of service. For example, it may specify the levels of availability, serviceability, performance, operation, or other attributes of the service like billing and even penalties in the case of violation of the SLA.
SME
|
Small to Medium-sized Enterprise or business.
SNMP (Simple Network Management Protocol)
|
The Internet standard protocol for managing nodes on an IP network.
SONET (Synchronous Optical Network)
|
A North American standard for using optical media as the physical transport for high-speed long-haul networks. SONET basic speeds start at 51.84 Mbps and go up to 2.5 Gbps.
SSH (Secure Shell)
|
A network protocol that allows data to be exchanged over a secure channel between two computers. Encryption provides confidentiality and integrity of data.
Subrate Multiplexer
|
At one end of a communications link, a device that combines several lower speed transmission channels into a single high speed channel. A multiplexer at the other end reverses the process. Sometimes called a mux. See Bit Interleaving/Multiplexer.
A digital transmission link with a capacity of 1.544 Mbps used in North America. Typically channelized into 24 DS0s, each capable of carrying a single voice conversation or data stream. Uses two pairs of twisted pair wires.
Combining (bonding) multiple PPP (Point-to-Point Protocol) links between two systems into one logical data pipe. MLPPP is a standard IETF protocol.
T3
|
A digital transmission link with a capacity of 45 Mbps, or 28 T1 lines.
TCP/IP (Transmission Control Protocol/Internet Protocol)
|
A protocol platform, known also as the Internet protocol suite, that combines both TCP and IP. Widely used applications, such as Telnet, FTP and SMTP, interface to TCP/IP.
TDM (Time Division Multiplexer)
|
A device which divides the time available on its composite link among its channels, usually interleaving bits (Bit TDM) or characters (Character TDM) of data from each terminal.
TDMoIP®
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TDM over IP is a standards-based transport technology that extends voice, video or data circuits across packet-switched networks simply, transparently and economically. Acting as a pseudowire, TDMoIP is unique in that it supports the multiple signaling standards, OAM mechanisms and clock recovery features demanded by TDM networks for carrying voice-grade telephony channels. A simple alternative to VoIP, TDMoIP enables using legacy TDM equipment while facilitating a smooth migration to newer IP, Ethernet and MPLS networks. TDMoIP technology was developed and patented by RAD, and is found in RAD’s IPmux, Vmux and Megaplex products.
Telnet
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The virtual terminal protocol in the Internet suite of protocols. It lets users on one host access another host and work as terminal users of that remote host. Instead of dialing into the computer, the user connects to it over the Internet using Telnet. When issuing a Telnet session, it connects to the Telnet host and logs in. The connection enables the user to work with the remote machine as though it were a terminal connected to it.
TETRA (Terrestrial Trunked Radio)
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A wireless communications standard for Professional Mobile Radio (PMR) and Private Access Mobile Radio (PAMR) applications. It is a digital format, i.e. speech is transmitted as binary data, which makes it far more difficult to monitor or eavesdrop.
Throughput
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The amount of information transferred through the network between two users in a given period, usually measured in the number of packets per second (pps).
Timeslot
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A portion of a serial multiplex of timeslot information dedicated to a single channel. In T1 and E1, one timeslot typically represents one 64 kbps channel.
Various methods and standards developed to ensure that accurate time and frequency is distributed in packet-based networks.
ToS (Type of Service) Field
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In a QoS scheme, an eight-bit field that lets values from 0 to 15 be assigned to request special handling of traffic (for example, minimize delay, maximize throughput). The ToS field is being phased out in favor of DSCP.
Traffic Contract
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An agreement between the user and the network management agent regarding the expected QoS provided by the network and the user’s compliance with the pre-determined traffic parameters (i.e. PCR, MBS, burstiness, average cell rate).
Traffic Policing
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Mechanism whereby any traffic which violates the traffic contract agreed to at connection setup, is detected and discarded.
Traffic Shaping
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A method for smoothing the bursty traffic rate that might arrive on an access virtual circuit so as to present a more uniform traffic rate on the network.
Transparent LAN Service (TLS)
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A high speed data service which allows for the interconnection of different LANs across an extended campus, metropolitan area or national network. Using VLANs and native LAN interfaces (such as 10/100 Mbps Ethernet), TLS provides a much simpler solution to the customer for connection of dispersed sites, than other forms of WAN, such as ATM or Frame Relay.
Trunk
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A single circuit between two points, both of which are switching centers or individual distribution points. A trunk usually handles many channels simultaneously.
UNI (User Network Interface)
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The interface, defined as a set of protocols and traffic characteristics, between the CPE and the ATM network.
VCAT (Virtual Concatenation)
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An inverse multiplexing technique used to split SDH/SONET bandwidth into logical groups, which may be transported or routed independently.
VLAN (Virtual LAN)
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A network architecture which allows geographically distributed users to communicate as if they were on a single physical LAN by sharing a single broadcast and multicast domain.
VLAN-Aware
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A device that is doing the Layer 2 bridging according to the VLAN tag in addition to the standard bridging parameters. A VLAN-aware device will not strip or add any VLAN header.
A mechanism specified in IEEE standard 802.1ad (“Provider Bridges”) to extend the IEEE VLAN tagging standard (802.1Q). Also known as double VLAN tagging or Q-in-Q, VLAN stacking allows service providers to assign service VLAN tags (S-VLAN) to Ethernet frames that are already marked with customer VLAN tags (C-VLAN), resulting in hierarchical or “stacked” VLAN tags.
VLAN Stripping
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Removal of VLAN tags from a network frame.
VoIP (Voice over IP)
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Set of facilities for managing the delivery of voice information using the Internet Protocol (IP). Voice information is sent in digital form in discrete packets over the Internet instead of in analog form over the public switched telephone network (PSTN). A major advantage of VoIP is that it avoids the tolls charged by ordinary telephone service.
VPLS (Virtual Private LAN Service)
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An IETF (Internet Engineering Task Force) proposal for providing Layer 2 VPNs that can support the connection of multiple sites in a single bridged domain over a managed IP/MPLS network. Edge routers, inter-connected by a full mesh of MPLS label switched path (LSP) “tunnels” through which run multiple pseudowires, enable any-to-any connectivity on a per-VPLS basis.
To the customer, all services in a VPLS appear to be on the same Ethernet LAN, regardless of actual geographic location. This removes complexity from enterprise networks, and lets carriers scale the networks.
VPN (Virtual Private Network)
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A restricted network that uses public wires to connect nodes. A VPN provides a way to encapsulate, or “tunnel,” private data cheaply, reliably, and securely through a public network, usually the Internet.
WAN (Wide Area Network)
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A network that typically spans nationwide distances and usually utilizes public telephone networks.
WDM (Wave Division Multiplexing)
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Optical transmission technique in which two or more wavelengths (each carrying its own information) are combined for transmission over a single optical fiber. At the receiving end, the wavelengths are separated and directed to separate receivers. Increases the capacity of data transmission over fiber optics. Also used to connect two fiber optic devices over a single strand of fiber.
ITU-T standard Y.1731 is an Ethernet OAM (operations, administration and maintenance) standard for testing an Ethernet service and for monitoring its performance.
IEEE standard 1588-2008, previously known as pre-standard 1588v2, is the latest version of Precision Time Protocol (PTP) for frequency and time of day distribution over packet switched networks. It is based on timestamp information exchange in a master-slave hierarchy.
IEEE standard 1588v2, also known as 1588-2008, is the latest version of Precision Time Protocol (PTP) for frequency and time of day distribution over packet switched networks. It is based on timestamp information exchange in a master-slave hierarchy.
IEEE standard 802.1ag, also known as “Connectivity Fault Management (CFM)”, is an Ethernet OAM (operations, administration and maintenance) standard for testing an Ethernet service over any path, whether a single link or end-to-end.
IEEE standard 802.3-2005, also known as 802.3ah clause 57, is an Ethernet OAM (operations, administration and maintenance) standard for testing the status of a single Ethernet link within a network. It is also known as Ethernet Link OAM and EFM (Ethernet in the First Mile) OAM.
